Recently, an electric vehicle and a fuel cell vehicle each having a motor used for driving a wheel, a hybrid vehicle having a motor and an engine each used for driving a wheel, and the like receive attention as a vehicle giving consideration to environment.
Such a vehicle is equipped with a large-capacity secondary battery used for driving a motor. The vehicle runs while monitoring a state-of-charge (SOC) of the secondary battery. In a case where the vehicle is an electric vehicle, a control device thereof notifies a driver to charge a secondary battery if necessary. In a case where the vehicle is a hybrid vehicle, a control device thereof starts up an engine, actuates a generator, and charges a secondary battery.
For example, Japanese Patent Laying-Open No. 2003-23703 discloses a hybrid vehicle that runs while monitoring a SOC.
As one of conditions for making hybrid vehicles widely available, common parts and units are used for various vehicle types. Meanwhile, a large-capacity secondary battery improves a running distance at one refueling, but increases a weight of a vehicle. Hence, an optimal capacity of the secondary battery must be selected in view of an economic aspect.
However, the selection of this optimal capacity is difficult due to a change in social realities (e.g., a change in price of gasoline), use conditions of a vehicle (e.g., frequency and necessity of a long distance run), and the like. In a region where gasoline is available inconveniently or a region where commercial power is inexpensive, moreover, charge of a secondary battery at home is realizable in addition to refueling.
A technology of secondary batteries advances remarkably, and a capacitance value per volume or per weight is improved gradually. In order to realize an efficient hybrid vehicle, it is advantageous that such an improved secondary battery is adopted.
As described above, if various hybrid systems are designed in correspondence with a change in capacity of a battery, there arises a problem that man-hours for development of a vehicle becomes large.